Change speed attachment



Jan. 31, 1956 P. LA HIRT CHANGE SPEED ATTACHMENT Filed Feb. 8, 1954 F15 El SPEED ATTACWENT Paul La Hirt, Chicago, Ill. Application `February 8, 1954, Serial No 408,767 Claims. (Cl. 3 2-23) This. invention relates to a dental engine and more partieu .rl engine- The dental enginez which isV a familiar instrument in a dentists oflice, drives a handpiece by an electric motor through ilegible belts which pass over pulleys carried by arms provided for universal movement of the handpiece. teel burrs are used for cutting in preparatory work to a .considerable amount in dental surgery and other operations .the oral cavity- The Speed at which such a steel burr is operated is dependent on the efficiency of the eutting within .the range which is comfortable for the patient- .Heating is particularly to be avoided lt has been found that afsteel burr driven at about .5,000 R- P- M.. best provides cutting without heating and without particular patient discornfiture Recently, carbide tipped bnrrs have been used.- The speed at which they do `the best cutting is exceedingly higher than that for steel burrs .An eiective speed'for carbide tipped burrs is around 11,090 R, 1- 'M- Very little heating occurs and no patient discomture although the cutting is much .faster- A problem exists `in the use. oi .the usual dental. engine tor cutting alternately with steel burrs and carbide tipped burra, While. the .carbide tip cuts much faster than the steel, the carbide tip can eut three times as fast if run. at 11,000 R. P. M. rather than 5,000. If the dental engine is converted by changing the pulleys .to provide ,for the higher speed, the use ofv the engine for steel tips is de- .st'r'oyed- Qn the other hand, if.- the carbide tipped burr is usedwith an engine which will drive the handpiece at .5,900 R- Pl M., the cutting will only be about one third as ,fast as could be accomplished and no particular ad- Vantage .is achieved.

The present invention provides a device .for easily and uuicklyconverting a dental engine to use either carbide or' .steel tipped burrs while using the .same motor speed and without risking running the pulley/son the .ilegible s oi -the engine at a speed conducive to Ytheir yearly iarlnre. The present .device is Secured to the usual dental engine adjacent the handpiece- This permits the pulleys between the attachment and the engine to run the .saine provided originally and to run at. a speed for which they were designed and at which they generally have a long life.- .A pr ferred embodiment-of the present invention is ile lnstrated in the accompanying drawings infwhich:

Figure 1 is a fragmentary side elevational view of a dental engine diagrammatically showing the mounting of the present device on an ann .of the engine;

. Figure 2 is a side elevational view "of the presentdeviceshovvn in mounted position upon a fragmentary por.- tion of an arm of the dental engine;l

Figure 3 is a front view of .the device;

Figure 4 Ais a rear vievtI ofA the-'device illustrated in figures .2 and 3; and

Figures 5, 6 and 7 are sectional views talgen respectively along lines 5 5, 6 6 and 7-'7 in Figure. 2,

y to a change speed attachment for a dental While this invention is susceptible of embodiments in 2,732,622 Patented JamY 3l, .1.356.

many difierent forms, there is shown in the drawings yand will herein be described in detail one `specific embodiment, with the understanding that the present disclosure is to be considered as an exemplilication ot the principles of the invention and is not intended to limit the invention to the embodiment illustrated The scope of the invention will be pointed out in the appended claims.

The dental engine illustrated in Figure 1 includes a supporting .standard 10 having a supporting yoke 11 at .the upper end- An electric motor 412. is pivotally supported. at the outer end .1.3 of the yolse and connected .for swinging movement about the outer end. along with an engine arm 14 extending outwardly from the end. of

.the yoke- A pair of pulleys 15, are mounted on the outer end of the engine arm. A flexible belt or cord drive A16 entends from a pulley .17 on the engine shaft outwardly over the pulleys l5 An intermediate arm 18 is oonnectcd by a swinging joint to the end of the engine arm `14 and carries a pair of pulleys .19 over which the belt .1.6 also passes. A third arm 2 0 extends from a pivotal con nection with arm 1 3 outwardly to a short anchored conn ection 21 with a handpiece 22. The belt 16 ordinarily entends from the motor to .the handpiece 22 to revolve a central part 23 in .the handpiece This central part. may receive cutting burrs or other rotary instruments normally used by dentists- A In the present. invention, the drive from. the motor l2 to the rotary part 23 ofthe handpieee is to an intermediate change speed attachment 24 secured on the arm .20. This change speed attachment .in essence comprises a compound pulley having a drive .sheave portion 25 over which the belt lo passes At least a pair ot driven sheave portions 26 and 27 are provided on the pulley-- and are of diiferent diameters to receive a driven b elt entending .from the .compound pulley to the rotary part 2 .of the handpiece The driven belt may thus be manually changed .from one sheave portion to the other of the ycompound pulley to eliect. a speed .change of the rotary part .in the handpiece. i

The drive belt i6 and driven belt eatending from the handpiece are each. of a flexible character perm. ting .some change .in their length without materially afi ng the driving .qualities ofthe belts The sheaves portion ,27 being of larger diameter than the smaller driven .sheave portion .2.6 requires the belt to stretch .in order to pass over the larger portion., T. hel tension in the belt is applied through this change speed attachment to the drive belt-lo and these tensions arc permitted to balance by virtue of the structure supporting the attachment The particular supporting structure includes a base .25 havinga central bore to receive thc prin .20 of the engine- A groove ,2,9 in the base slidipgly receives a. 30 .held parallel to the arm 20 by a pair ot clamp bers `31 and 32- .These clamp members are spaced apart a distance in excess oi the longitudinal length of .the base so that .the base may slide between the clamp members. This sliding permits an equalization of .the ,tension in the ,drive and driven b elts when the latter-Wis' changed f oni on'drivensheave portionto another. .Y .A

The lparticular structure .for supporting .the compound pulley includes a stud 33, secured .in the base portion, upon which the compound pulley is idly mounted and .held in place .by a thumb nut 3.5. 'lhe pulley may be provided with a bronge sleeve 36 running against a washer 37 adjacent the base.

It is desirable in some instances to lock the base portion tothe arm aftera change .in the driving relation has .be 'triade by moving thedrivonbelt sheave portion.; After the belts ay .equalized the tension by shifting the positie.. of .the pound pulley along the arm ..20Qthe pulley may be loclt'ed portion'39 of the base tightly against the arm 20 and rod 30. After such tightening, the compound pulley will remain in position. lf a change in the speed of the device is desired after the pulley has been tightened in position, it should be loosened to permit the belts to automatically adjust the position of the pulley to equalize the tension.

Portions of the compound pulley may be selected to attain the desired speeds. In the preferred embodiment illustated, the driven portion 26 of the pulley will produce the normal 5,000 R. P. M. for the rotary part of the handpiece. The larger driven portion 27 has a diameter such that the speed of the rotary part may be increased to 11,000 R. P. M. While maintaining the same motor speed. By the use of the present invention, the pulleys between the change speed attachment and the motor are not required to run faster than their original design called for and yet the rotary part of the handpiece may be driven at a much faster rate.

Dentists may convert their present dental engines very simply by attaching the present attachment, permitting them to use a single engine most eiectively with both steel and carbide tipped burrs. The eticiency of the necessary cutting operations can thus be improved without a major change in the dental engines which might otherwise be required. The incorporation of the present attachment may be easily made in most dental engines by removing the arm 20 so that one end is exposed to permit the base 28 to be passed over the arm lengthwise to a chosen position along the arm. The clamps 32 and 33 may be applied to the arm in any desired position by merely tightening the associated screws. The time required for making the attachment is negligible. At the same time, the cost of the attachment is small, particularly compared with the increased eiciency and tiexibility it permits in the use of an existing dental engine.

I claim:

1. A change speed attachment for a dental engine having a driving motor, adjustable arms carrying fiexible belt driving means and a hand piece having a driven rotary part, comprising: a rotatable compound pulley having a base and mounted upon one adjustable arm for sliding movement longitudinally of the arm clamp, clamp means secured to the arm on each side of the pulley for limiting said sliding movement to a portion of the length of the arm, means secured to the arm and slidingly engaging a portion of said pulley base to hold the pulley against rotation about the arm, a drive belt means passing over one portion of the pulley and connected to said motor for driving the pulley, said pulley having other portions of different diameter and a driven belt means selectively placeable on said other portions to vary the driven speed thereof, said compound pulley automatically adjusting its position along the arm under tension of t said belt drive and driven means, said driven belt means being connected in driving relation with the rotary part of the hand piece to provide dilerent speeds of the rotary part without changing motor speed.

2. A change speed attachment for a dental engine having a motor and swingably adjustable arms carrying flexible belt driving means for rotating a part of a hand piece comprising: an elongated rod member having a clamp member at each end adapted to clamp upon one arm of the dental engine adjacent the hand piece and to position the rod substantially parallel to said arm; a cornpound pulley having a supporting shaft and a base member with the pulley idly rotatable on the supporting shaft, said base member having a bore passing therethrough and an outer groove parallel to the bore embracing said elongated rod and slidable therealong between the clamp members, said base member bore being adapted to receive said arm of the dental engine upon which the clamps are placed with said groove holding the base member against rotation upon the arm, said pulley having a drive sheave and a pair of driven sheave portions of different diameter so that the driven flexible belt driving means may be selectively placed on either of said driven sheave portions to change the speed of the hand piece part without changing the motor speed, and a lock member on the base member for securing the base in an immovable position on the arm between said clamp members.

3. A change speed attachment for a dental engine having a motor, swingably adjustable arms carrying flexible belt driving means and a hand piece having a rotary part, comprising: a base member having a longitudinal bore mounting the base member on one arm.of said dental engine with said arm passing through the bore; a guide rod clamped to said arm and having a portion engaging the base member to prevent relative rotation between the arm and base member; a compound pulley secured to the base member and having a drive sheave and at least a pair of driven sheaves of differentdiameters, a drive belt means connected with the motor and passing over the drive sheave of said pulley; and a driven belt means connected with the rotary part of the hand piece and selectively placeable upon either of said driven sheaves to vary the speed of said rotary part with a single motor speed.

4. A change speed attachment for a dental engine having a motor, swingably adjustable arms carrying ilexible belt driving means and a hand piece having a rotary part, comprising: an elongated rod member having a clamp member at each end adapted to clamp upon one arm of said dental engine adjacent the hand piece to hold the rod substantially parallel to the arm; a base member having a bore with said arm passing therethrough and an outer groove parallel to the bore for embracing said rod to hold the base against rotation on the arm, said base member being mounted between said clamp members, an outwardly extending stub shaft on the base member and a compound pulley idly rotatable on the shaft, said pulley having a drive sheave portion and a pair of driven sheave portions of different diameter so that the driven ilexible belt driving means may be selectively placed on either of said driven sheave portions to change the speed of the hand piece part without changing the motor speed.

5. A change speed attachment for a dental engine having a motor, swingably adjustable arms carrying flexible belt driving means and a hand piece having a rotary part, comprising: an elongated rod member having a clamp member at each end adapted to clamp upon one arm of said dental engine adjacent the hand piece to hold the rod substantially parallel to the arm; a base member having a bore with said arm passing therethrough and an outer groove parallel to the bore for embracing said rod to hold the base against rotation on the arm, said base member being mounted between said clamp members, an outwardly extending stub shaft on the base member and a compound pulley idly rotatable on the shaft, said pulley having a drive sheave portion and a pair of driven sheave portions of different diameter so that the driven exible belt driving means may be selectively placed on either of said driven sheave portions to change the speed of the hand piece part without changing the motor speed, said base member and pulley being slidable on the arm be'- tween said clamp members and automatically adjusting its position between said clamp members under tension of said belt driving means, and a lock member for securing the base immovable relative to said arm after such automatic adjustment.

References Cited in the tile of this patent UNITED STATES PATENTS Browne Aug. 16, 1887 

